Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations. The term wastewater includes “sewage,” which is wastewater including feces and/or urine. “Sewage” includes domestic, municipal, or industrial liquid waste products disposed of, usually via a pipe or sewer or similar structure, sometimes in a cesspool emptier.
The precise composition of wastewater varies depending on the source. All wastewater consists mostly of water, which is often added during flushing to carry waste down a drain. Wastewater also may contain pathogens (such as bacteria, viruses, prions and parasitic worms), non-pathogenic bacteria, organic materials (such as feces, hairs, food, vomit, paper fibers, plant material, humus, urea, fruit sugars, soluble proteins, drugs, drug metabolites), inorganic particulate matter (such as sand, grit, metal particles, ceramics, etc), soluble inorganic material (such as ammonia, road salt, sea salt, cyanide, hydrogen sulfide, thiocyanates, thiosulfates), animals (such as protozoa, insects, arthropods, small fish, etc.), macro-solids (such as sanitary napkins, diapers), gases (such as hydrogen sulfide, carbon dioxide, methane, etc.), emulsions (such as paints, adhesives, mayonnaise, hair colorants, emulsified oils, etc.), pesticides, herbicides, etc.
Many of the above listed wastewater components degrade by oxidative pathways. The oxidation can be aerobic and/or anaerobic. The oxidation can take place either with or without biologic (e.g., bacterial) participation. In either case, the oxidation demands oxygen (either directly or indirectly) as a reactant. Accordingly, as wastewater components are degraded, oxygen is consumed. In a very general sense the degradation of wastewater adheres to the following formula:“Oxidizable wastewater materials”+O2→CO2+H2O+“oxidized products”
Some oxidizable wastewater materials comprise nitrogen. Some oxidized products comprise nitrogen. Total Kjeldahl Nitrogen (TKN) is the sum of organic nitrogen, ammonia (NH3), and ammonium (NH4+) in wastewater. Total Nitrogen (TN) also includes the nitrate and nitrite in the wastewater. Accordingly, one may calculate TN by adding the concentrations of nitrate and nitrite to TKN.
Some oxidizable wastewater materials comprise phosphorous. Some oxidized products comprise phosphorous. Phosphorus may be found in several forms, including dissolved form (orthophosphate), inorganic form (reactive plus condensed or acid hydrolysable phosphate) and organically bound forms. Total Phosphorus is the sum of reactive, condensed and organic phosphorous.
Almost any component of wastewater will initiate oxidation. The amount of oxygen consumed in the process of oxidizing the oxidizable wastewater materials can be measured in commercial laboratories as the Biochemical Oxygen Demand (BOD). Such chemicals are also liable to be broken down using strong oxidizing agents and these chemical reactions create what is measured in the laboratory as the Chemical Oxygen Demand (COD). Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of potential pollution. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of oxidizable pollutants (not necessarily limited to biodegradable components).
The 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the Ultimate BOD. There are also many different COD tests of which the 4-hour COD is probably the most common.
The laboratory test procedures for the determining the above oxygen demands are detailed in many standard texts, including the Standard Methods For the Examination Of Water and Wastewater, published jointly by the American Public Health Association, the American Waters Works Association, and the Water Environment Association.
Total Suspended Solids (TSS) refers to solids in water (mg/L) that can be trapped by a filter. TSS can include a wide variety of material, such as sand, silt, decaying plant and animal matter, industrial wastes, etc. High concentrations of suspended solids can cause many problems for stream health and aquatic life. To measure TSS, the water sample is filtered through a pre-weighed filter. The residue retained on the filter is dried in an oven at 103 to 105° C. until the weight of the filter no longer changes. The increase in weight of the filter represents the total suspended solids. TSS can also be measured by analyzing for total solids (TS) and subtracting total dissolved solids (TDS).
Various wastewater treatment systems and methods of treating wastewater are available in the marketplace. Some of these are extolled as substantially reducing the TSS, TN, and/or BOD in wastewater effluent. As used herein, the term “effluent” (e.g., wastewater effluent) refers to the liquid aqueous material discharged from the wastewater treatment system, back into the surrounding environment. In one example, the effluent would be the liquid aqueous material drained from the wastewater treatment system through a pipe and into a nearby creek.
One system showing reductions in TSS, TN, and BOD is the Aerocell Self Contained Advance Treatment System, sold by Quanics, Inc. (“the Quanics System”), advertises a 5-day BOD of 2 mg/L, TSS of 2 mg/L, and a TN or 9 mg/L. This system is certified by the NSF under ANSI Standard 40. Standard 40 is for residential wastewater treatment systems having rated capacities between 400 gallons (1514 Liters) and 1500 gallons (5678 Liters) per day. Accordingly, the Quanics system would be expected to demand at least 3028 mg/day of oxygen from the surrounding environment. The system should also be expected to release about 3 grams/day of TSS, about 15 grams/day of TN, and about 1500 kilograms/day of water into the surrounding environment through effluent.
Quanics also offers a Bio-COIR system, which is advertised as providing a 5-day BOD of 9 mg/L, TSS of 12 mg/L, and a TN or 17 mg/L.
While the commercial systems available on the market reduce BOD, TSS, and TN, they still release contaminants that demand oxygen from the environment. These systems release some nitrogenous waste and some phosphorous waste. They also release solid waste material into the environment. They release large quantities of water into the environment.
Releasing oxygen-demanding contaminants into the environment is particularly undesirable in wetland areas. The oxygen demanded by wastewater contaminants lessens the oxygen available for wildlife.
Releasing nitrogenous waste into the environment is also particularly undesirable in wetland areas. Such nitrogenous compounds (e.g., nitrates and nitrites) can feed certain types of organisms, which leads to overpopulation of those organisms.
Despite advances in the wastewater treatment arts, a continuing need exists for reducing BOD, TN, and TSS in effluent wastewater.
As noted above, many wastewater treatment systems produce a substantial quantity of liquid water waste. In some circumstances it is desirable to reduce the amount of water drained into the surrounding area. Accordingly, the wastewater treatment arts also have a need for systems and methods providing for reducing the amount of liquid water discharged.